initial commit, derived from iTot Apps ITFacebookManager for AppsGuild.
this is a slimmed-down version of the installation attribution logic found in the official Facebook iOS SDK at https://github.com/facebook/facebook-ios-sdk, specifically the logic in https://github.com/facebook/facebook-ios-sdk/blob/master/src/FBUtility.m#L358-L403 which is called by https://github.com/facebook/facebook-ios-sdk/blob/master/src/FBSettings.m#L371-L387. If you are only interested in running Facebook Mobile App Install Ad Campaigns, this is all the Facebook SDK logic you should need.